1. Field of the Invention
This invention relates to a method for cleaning sheet materials such as photographic films or the wafers used in integrated circuit production, and to various embodiments of a device for practicing the method.
2. Description of the Prior Art
Thorough removal of dust particles from sheets is often necessary for proper utilization of the sheet. For example, thorough removal of dust particles from photographic film such as a negative or a lantern slide is necessary to produce high quality prints, particularly when an enlarged print is to be made. Also, dust particles must be thoroughly removed from the surfaces of metal oxide semi-conductor wafers on which integrated circuits are to be formed, or the dust may cause imperfections in the circuits.
The prior art is replete with sheet cleaning devices. Illustrative examples include those described in U.S. Pat. Nos. 1,162,812, 1,389,082, 1,401,012, 3,128,492, 3,149,356, 3,453,681, 3,641,605, 3,644,953, and German Auslegeschrift No. 1,077,960. These devices can, with varying degrees of effectiveness, remove foreign particles from sheets such as photographic film. The cleaning methods performed by these devices, however, have had certain limitations or presented certain problems which restrict their efficiency or adaptability for the cleaning of certain types of sheets.
For example, the devices suggested in most of the aforementioned U.S. patents wipe or brush the surface of the sheet. Such cleaning action presents the possibility that the sheet may be scratched by foreign particles trapped in the wiping member, or that lint from the wiping member itself will be left on the film, or, in the case of brushing, that a portion of the removed dust will again settle on the cleaned sheet.
German Auslegeschrift No. 1,077,960, considered the closest prior art to the present invention, suggests a pair of cleaning rollers which have sufficient surface attraction so that the surface of the roller can contact and remove foreign particles from the surfaces of a sheet to be printed. The rollers roll over the surface of the sheet to be cleaned, thereby eliminating the aforementioned problems with wiping or brushing of the sheet. The dust collected on the cleaning roller of this device, however, is removed by a damp wiping of the cleaning roll surface, which, if the device were used with photographic film, would present the possibility that the cleaning liquid could be carried into contact with and damage the film. Also, there is no teaching in this German patent of a cleaning roll structure which affords the cleaning of lantern slides (e.g. conventional 35 millimeter lantern slides) wherein the film for which surface cleaning is desired is laminated in a surrounding frame which projects from both surfaces of the film.